Cells and microscopy

• State the two types of cell


  Eukaryotic (animals and plants) and prokaryotic.
• What is the difference between a eukaryotic and a prokaryotic cell?

  A eukaryotic cell contains membrane-bound organelles. A prokaryotic cell does not.
• List the components of both plant and animal cells

  • Nucleus

  • Cytoplasm

  • Cell membrane

  • Mitochondria

  • Ribosomes
• How is genetic information stored in a eukaryotic cell?


  Within the nucleus. arranged in chromosomes.
• Other than storing genetic information, what is the function of the nucleus?

  Controls cellular activities
• Describe the structure of the cytoplasm


  • Fluid component of the cell

  • Contains organelles, enzymes and dissolved ions and nutrients
• What is the function of the cytoplasm?


  Site of cellular reactions e.g. first stage of respiration
• How is genetic information stored in a prokaryotic cell?

  Found free within the cytoplasm as —>

  • Chromosomal DNA (single large loop of circular DNA)
  • Plasmid DNA
• List the organelles found in prokaryotic cells

  • Chromosomal DNA
  • Plasmid DNA
  • Cell wall
  • Cell membrane
  • Ribosomes
  • Flagella
• What is the function of the chloroplasts?

  Site of photosynthesis
• When looking at a cell using a light microscope, why do chloroplasts appear green?

  Contain chlorophyll, a green pigment
• What does the permanent vacuole contain?


  A solution of salts, sugars and organic acids
• What is the function of the permanent vacuole?


  Supports the cell, maintaining its turgidity
• What is the cell wall made of?

  Cellulose
• What is the function of the cell wall?


  • Provides strength
  • Prevents the cell bursting when water enters by osmosis
• What is the function of the ribosomes?


  Joins amino acids in a specific order during translation
• Which organelles are found in plant cells only? 


  • Large, permanent vacuole
  • Cell wall
  • Chloroplasts
• What is the function of the cell membrane?


  Controls the entry and exit of materials into and out of the cell
• What is the function of the mitochondria?

  Site of later stages of aerobic respiration in which ATP is produced
• How do you convert from m to pm?

  × 1 000 000 000 000 (× 1012)
• How to you convert from nm to m?


  ÷ 1 000 000 000 (× 10-9)
• How do you convert from m to um?

  × 1 000 000 (x 106)
• How do you convert from m to nm?

  × 1 000 000 000 (x 109)
• What are the disadvantages of electron microscopes?


  • Expensive
  • Large so less portable
  • Require training to use
  • Only dead specimens can be observed
• How do you convert from m to mm?

  × 1000 (× 103)
• Why do electron microscopes have a greater magnification and resolution?

  They use a beam of electrons which has a shorter wavelength than photons of light
• How have electron microscopes enabled scientists to develop their understanding of cells?

  • Allow small sub-cellular structures (e.g. mitochondria, ribosomes) to be observed in detail
  • Enable scientists to develop more accurate explanations about how cell structure relates to function
• Name the two types of electron microscope

  • Transmission electron microscope (TEM)

  • Scanning electron microscope (SEM)
• What is the advantage of electron microscopes?


  Greater magnification and resolution
• What is the disadvantage of light microscopes?


  Limited resolution
• How does an electron microscope work?


  It uses a beam of electrons which are focused using magnets. The electrons hit a fluorescent screen which emits visible light, producing an image.
• How does a light microscope work?


  Passes a beam of light through a specimen which travels through the eyepiece lens, allowing the specimen to be observed.
• What are the advantages of light microscopes?


  • Inexpensive
  • Easy to use
  • Portable
  • Observe both dead and living specimens
• What is resolution?


  The smallest distance between two objects that can be distinguished
• How can the magnification of an image be calculated?


  Magnification = Image size / Object size
• Describe the function of ciliated epithelial cells lining the airways


  Move in synchronised waves to beat mucus (containing dirt and pathogens) up to the back of the throat where it can be swallowed.
• What is magnification?


  The number of times bigger an image appears compared to the size of the specimen
• Describe how sperm cells are adapted to their function


  • Haploid nucleus contains genetic information
  • Tail enables movement
  • Mitochondria provide energy for tail movement
  • Acrosome contains enzymes that digest the egg cell membrane
• Where are ciliated epithelial cells found?

  Found lining the surface of structures such as the respiratory tract and uterus.
• Describe sexual reproduction in terms of chromosome number


  • Two haploid gametes fuse
  • Resulting embryo has two chromosomes for each gene and two copies of each allele
  • Diploid